collab: Setup database for LLM service (#15882)

This PR puts the initial infrastructure for the LLM service's database
in place.

The LLM service will be using a separate Postgres database, with its own
set of migrations.

Currently we only connect to the database in development, as we don't
yet have the database setup for the staging/production environments.

Release Notes:

- N/A

crates/collab/src/migrations.rs

@@ -0,0 +1,49 @@
+use std::path::Path;
+use std::time::Duration;
+
+use anyhow::{anyhow, Result};
+use collections::HashMap;
+use sea_orm::ConnectOptions;
+use sqlx::migrate::{Migrate, Migration, MigrationSource};
+use sqlx::Connection;
+
+/// Runs the database migrations for the specified database.
+pub async fn run_database_migrations(
+    database_options: &ConnectOptions,
+    migrations_path: impl AsRef<Path>,
+    ignore_checksum_mismatch: bool,
+) -> Result<Vec<(Migration, Duration)>> {
+    let migrations = MigrationSource::resolve(migrations_path.as_ref())
+        .await
+        .map_err(|err| anyhow!("failed to load migrations: {err:?}"))?;
+
+    let mut connection = sqlx::AnyConnection::connect(database_options.get_url()).await?;
+
+    connection.ensure_migrations_table().await?;
+    let applied_migrations: HashMap<_, _> = connection
+        .list_applied_migrations()
+        .await?
+        .into_iter()
+        .map(|migration| (migration.version, migration))
+        .collect();
+
+    let mut new_migrations = Vec::new();
+    for migration in migrations {
+        match applied_migrations.get(&migration.version) {
+            Some(applied_migration) => {
+                if migration.checksum != applied_migration.checksum && !ignore_checksum_mismatch {
+                    Err(anyhow!(
+                        "checksum mismatch for applied migration {}",
+                        migration.description
+                    ))?;
+                }
+            }
+            None => {
+                let elapsed = connection.apply(&migration).await?;
+                new_migrations.push((migration, elapsed));
+            }
+        }
+    }
+
+    Ok(new_migrations)
+}